3 research outputs found
Resolving Marker Pose Ambiguity by Robust Rotation Averaging with Clique Constraints
Planar markers are useful in robotics and computer vision for mapping and
localisation. Given a detected marker in an image, a frequent task is to
estimate the 6DOF pose of the marker relative to the camera, which is an
instance of planar pose estimation (PPE). Although there are mature techniques,
PPE suffers from a fundamental ambiguity problem, in that there can be more
than one plausible pose solutions for a PPE instance. Especially when
localisation of the marker corners is noisy, it is often difficult to
disambiguate the pose solutions based on reprojection error alone. Previous
methods choose between the possible solutions using a heuristic criteria, or
simply ignore ambiguous markers.
We propose to resolve the ambiguities by examining the consistencies of a set
of markers across multiple views. Our specific contributions include a novel
rotation averaging formulation that incorporates long-range dependencies
between possible marker orientation solutions that arise from PPE ambiguities.
We analyse the combinatorial complexity of the problem, and develop a novel
lifted algorithm to effectively resolve marker pose ambiguities, without
discarding any marker observations. Results on real and synthetic data show
that our method is able to handle highly ambiguous inputs, and provides more
accurate and/or complete marker-based mapping and localisation.Comment: 7 pages, 4 figures, 4 table
Effect of marker position and size on the registration accuracy of HoloLens in a non-clinical setting with implications for high-precision surgical tasks
Acknowledgments: We are grateful to Mike Whyment for the purchase of the holographic headset used in this study and to Rute Vieira and Fiona Saunders for their advice on statistics. We would also like to thank Denise Tosh and the Anatomy staff at the University of Aberdeen for their support. This research was funded by The Roland Sutton Academic Trust (RSAT 0053/R/17) and the University of Aberdeen (via an Elphinstone Scholarship, IKEC Award and Medical Sciences Honours project funding). Funding: This study was funded by The Roland Sutton Academic Trust (RSAT 0053/R/17) and the University of Aberdeen (via an Elphinstone Scholarship, IKEC Award and Medical Sciences Honours project funding).Peer reviewedPublisher PD
Geometric Inference with Microlens Arrays
This dissertation explores an alternative to traditional fiducial markers where geometric
information is inferred from the observed position of 3D points seen in an image. We offer an alternative approach which enables geometric inference based on the relative orientation
of markers in an image. We present markers fabricated from microlenses whose appearance
changes depending on the marker\u27s orientation relative to the camera. First, we show how
to manufacture and calibrate chromo-coding lenticular arrays to create a known relationship
between the observed hue and orientation of the array. Second, we use 2 small chromo-coding lenticular arrays to estimate the pose of an object. Third, we use 3 large chromo-coding lenticular arrays to calibrate a camera with a single image. Finally, we create another type of fiducial marker from lenslet arrays that encode orientation with discrete black and white appearances. Collectively, these approaches oer new opportunities for pose estimation and camera calibration that are relevant for robotics, virtual reality, and augmented reality